Nine of the last twelve standard supermarket eggs I’ve cracked open had double yolks. I’m not sure I’ve ever seen even a single egg like this before.

What could this mean? Is it another sign of an impending Armageddon?

3 double-yolk eggs and 1 single-yolk eggs in a frying pan

(Photo by Chris J Walker on Unsplash)

Well, tradition-wise, there’s a variety of options depending on your affiliations. At least according to Sauder’s Eggs:

  • Norseman thought that double-yolk eggs meant someone in your family is going to die. Oh dear.
  • Wiccans believed that it’s a sign of future good fortune for the egg-cracker. I think I’d prefer to go with this one.
  • In some cultures, it’s supposedly a sign that a someone you know (or you yourself) is going to become pregnant.

How often do double-yolks occur? Well according to Dr Karl Kruszelnicki, if you average out the rates from chickens of all ages than 1 in 1000 eggs would have two yolks. So have a experienced a one in many many trillion life event - far rarer than a lottery win?

Well, not necessarily. The way modern egg-farming works means that at a box level double-yolks are not an a statistically independent phenomenon. Eggs of a certain size, from hens of a certain breed or age, or those having experienced certain patterns of light exposure are more likely to be doubles. And distribution networks tend to box up eggs by size and flock - so if you find one you’re much more likely to find another.

This is to the extent that M&S started offering boxes of 100% guaranteed double yolkers for sale. Admittedly at a cost, because to satisfy the guarantee the eggs needed to be “candled” first.

Besides 9 out of 12 isn’t anywhere near the most extreme recorded case. One of my fellow countryfolk apparently once opened a continuous sequence of 29 out of 29 double-yolked eggs (not, of course, from guaranteed double-yolk boxes, that would be even more irrelevant news than this post). And as for a single egg, well, the current world record appears to be an egg that contained an astonishing nine yolks.